1. Chapter 9 -- Problem 25:

process p
const w
var na, ns, i, nr, j : integer, {init. 0}
    akn: boolean {init. false}
begin

   na+w>ns -> send data(ns, nr) to q; ns:=ns+1; akn := false

[] rcv data(i,j) from q -> na:=max(na,j);
                           if true -> skip
                           [] i<nr -> akn:=true
                           [] nr=i -> {accept data} nr:=nr+1; akn := true
                           fi

[] akn -> send ack(nr) to q; akn := false

[] rcv ack(j) from q -> na := max(na,j)

[] timeout (na<ns ^ #ch.p.q+#ch.q.p=0 ^ ~akn.q) -> send data(na, nr) to q

[] rcv error from q -> skip

end 

(Note: You will receive full credit even your solution doesn't have
       the third and the fourth actions.)

2. Chapter 11 -- Problem 10

process p[i:0..n-1]
var up: boolean,
    b : 0..1
begin

   rcv chk(b) from p[i -n 1] -> if i  = 0 -> b:=1
                                [] i != 0 -> skip
                                fi;
                                send chk(b) to p[i +n 1];

                                if b=0 -> up := false
                                [] b=1 -> up := true
                                fi

[] rcv error from p[ i -n 1] -> skip

[] timeout (for every k, 0<=k<=n-1, #ch.p[k].p[k + n 1] = 0) ->
                                if i  = 0 -> send chk(0) to p[i +n 1]
                                [] i != 0 -> skip
                                fi; up:=false

end

3. Chapter 11 -- Problem 24

The protocol remains the same as in Section 11.3 except for the following changes:

1. Each message is of the form st(i, vp) where vp is the value of variable
   vp in p[i] when p[i] generates this message.

2. Remove variables ts and t from each process.